Abstract:

A planar heater includes a planar supporter, two electrodes and a heating
element. The heating element is supported by the planar supporter and
electrically connected to the two electrodes. The heating element
includes at least one carbon nanotube structure and a matrix. The at
least one carbon nanotube structure includes a carbon nanotube film
including of a plurality of carbon nanotubes entangled with each other.

Claims:

1. A planar heater comprising:a planar supporter;two electrodes;a heating
element supported by the planar supporter and electrically connected to
the two electrodes, the heating element comprising at least one carbon
nanotube structure and a matrix enclosing the at least one carbon
nanotube structure therein; wherein the at least one carbon nanotube
structure comprises a carbon nanotube film, the carbon nanotube film
comprises of a plurality of carbon nanotubes entangled with each other.

2. The planar heater of claim 1, wherein the planar supporter and the
matrix are flexible.

3. The planar heater of claim 1, further comprising two wires, each wire
is connected to one of the two electrodes; and the wires extend outside
of the matrix.

4. The planar heater of claim 1, wherein the carbon nanotube film consists
of a substantially pure film of carbon nanotubes.

5. The planar heater of claim 1, wherein the two electrodes are located on
a top surface of the heating element and spaced apart from each other.

6. The planar heater of claim 1, further comprising a heat-reflecting
layer disposed on a top surface of the planar supporter, and the heating
element is disposed on a top surface of the heat-reflecting layer.

8. The planar heater of claim 6, further comprising a protecting layer
disposed on a top surface of the heating element.

9. The planar heater of claim 1, wherein the at least one carbon nanotube
structure comprises two or more carbon nanotube films stacked, coplanar
or both stacked and coplanar with each other.

10. The planar heater of claim 1, wherein the carbon nanotube film defines
a plurality of micropores and the matrix is dispered into the micropores.

11. The planar heater of claim 10, wherein the diameter of the micropores
is less than 10 μm.

12. The planar heater of claim 1, further comprising a heat-reflecting
layer disposed on a surface of the planar supporter, and the heating
element and the heat-reflecting layer are disposed on opposite sides of
the planar supporter.

13. An apparatus comprising a planar heater, the planar heater
comprising:two spaced electrodes; anda heating element electrically
connected to the two electrodes, the heating element comprising a carbon
nanotube structure and a matrix strengthening the carbon nanotube
structure;wherein the carbon nanotube structure comprises a carbon
nanotube film, the carbon nanotube film comprises a plurality of carbon
nanotubes entangled with each other.

14. The apparatus of claim 13, wherein the two electrodes are located
within the matrix.

15. The apparatus of claim 14, further comprising a heat-reflecting layer
and a protecting layer, wherein the heat-reflecting layer and the
protecting layer are located on opposite surfaces of the heating element,
and the heat-reflecting layer and the protecting layer are outermost
surfaces of the planar heater.

16. The apparatus of claim 15, wherein the planar heater is flexible.

17. The apparatus of claim 13,, wherein a plurality of micropores is
defined by adjacent carbon nanotubes and the matrix is dispersed in the
micropores.

18. A planar heater comprising:two electrodes; anda heating element
electrically connected to the two electrodes, the heating element
comprising at least one flocculated carbon nanotube film and a matrix
covering the at least one flocculated carbon nanotube film.

19. The planar heater of claim 18, wherein the at least one flocculated
carbon nanotube film comprises a plurality of micropores and the matrix
is further located in the micropores.

20. The planar heater of claim 1, wherein the carbon nanotube film is a
flocculated carbon nanotube film.

Description:

RELATED APPLICATIONS

[0001]This application is a continuation application of U.S. patent
application Ser. No. 12/655,507, filed Dec. 31, 2009 entitled "CARBON
NANOTUBE HEATER" the disclosure of which is incorporated by reference.

[0005]Heaters are configured for generating heat. According to the
structures, the heaters can be divided into three types: linear heater,
planar heater and hollow heater.

[0006]The linear heater has a linear structure, and is a one-dimensional
structure. An object to be heated can be wrapped by the linear heater
when the linear heater is used to heat the object. The linear heater has
an advantage of being very small in size and can be used in appropriate
applications.

[0007]The planar heater has a planar two-dimensional structure. An object
to be heated is placed near the planar structure and heated. The planar
heater provides a wide planar heating surface and an even heating to an
object. The planar heater has been widely used in various applications
such as infrared therapeutic instruments, electric heaters, etc.

[0008]The hollow heater defines a hollow space therein, and is
three-dimensional structure. An object to be heated can be placed in the
hollow space of the hollow heater. The hollow heater can apply heat in
different directions about an object and will have a high heating
efficiency. Hollow heaters have been widely used in various applications.

[0009]A typical heater includes a heating element and at least two
electrodes. The heating element is located on the two electrodes. The
heating element generates heat when a voltage is applied to it. The
heating element is often made of metal such as tungsten. Metals, which
have good conductivity, can generate a lot of heat even when a low
voltage is applied. However, metals may be easily oxidized, thus the
heater element has a short life. Furthermore, since metals have a
relative high density, the heating element made of metals are heavy,
which limits applications of such heater.

[0010]What is needed, therefore, is a heater based on carbon nanotubes
that can overcome the above-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]Many aspects of the embodiments can be better understood with
reference to the following drawings. The components in the drawings are
not necessarily drawn to scale, the emphasis instead being placed upon
clearly illustrating the principles of the embodiments. Moreover, in the
drawings, like reference numerals designate corresponding parts
throughout the several views.

[0012]FIG. 1 is an isotropic view of one embodiment of a planar heater
having a carbon nanotube structure.

[0013]FIG. 2 is a schematic, cross-sectional view, along a line 2-2 of
FIG. 1.

[0015]FIG. 4 is a schematic view of a carbon nanotube segment in the drawn
carbon nanotube film of FIG. 3.

[0016]FIG. 5 is an SEM image of a flocculated carbon nanotube film.

[0017]FIG. 6 is an SEM image of a pressed carbon nanotube film.

[0018]FIG. 7 is an SEM image of an untwisted carbon nanotube wire.

[0019]FIG. 8 is an SEM image of a twisted carbon nanotube wire.

[0020]FIG. 9 is a schematic view of one embodiment of an untwisted linear
carbon nanotube structure.

[0021]FIG. 10 is a schematic view of one embodiment of a twisted linear
carbon nanotube structure.

[0022]FIG. 11 is a schematic view of a planar heater, wherein the heating
element is a single linear carbon nanotube structure.

[0023]FIG. 12 is a schematic view of a planar heater, wherein the heating
element includes a plurality of parallel linear carbon nanotube
structures.

[0024]FIG. 13 is a schematic view of a planar heater, wherein the heating
element includes a plurality of woven linear carbon nanotube structures.

[0025]FIG. 14 is a schematic view of a planar heater, wherein the heating
element includes a plurality of spaced carbon nanotube structures.

[0026]FIG. 15 is an SEM image of a fracture surface of one embodiment of
the heating element.

[0027]FIG. 16 is a schematic, cross-sectional view of one embodiment of a
planar heater having a carbon nanotube structure.

[0028]FIG. 17 is a relationship of one embodiment of temperature and time
of a planar heater.

[0029]FIG. 18 is a flow chart of a method of one embodiment for
fabricating a planar heater.

[0030]FIG. 19 is an isotropic view of one embodiment of a hollow heater
having a carbon nanotube structure.

[0031]FIG. 20 is a schematic, cross-sectional view, along a line 20-20 of
FIG. 19.

[0032]FIG. 21 is a schematic, cross-sectional view, of one embodiment of a
hollow heater.

[0033]FIG. 22 is a schematic, cross-sectional view, of one embodiment of a
hollow heater.

[0034]FIG. 23 is an isotropic view of a hollow heater, wherein the heating
element is a single linear carbon nanotube structure.

[0035]FIG. 24 is an isotropic view of a hollow heater, wherein the heating
element includes a plurality of parallel linear carbon nanotube
structures.

[0036]FIG. 25 is an isotropic view of a hollow heater, wherein the heating
element includes a plurality of woven linear carbon nanotube structures.

[0037]FIG. 26 is an isotropic view of one embodiment of a hollow heater.

[0038]FIG. 27 is an isotropic view of one embodiment of a hollow heater.

[0039]FIG. 28 is a flow chart of a method of one embodiment for
fabricating a hollow heater.

[0040]FIG. 29 is an isotropic view of other embodiment of a hollow heater
having a carbon nanotube structure.

[0041]FIG. 30 is a schematic, cross-sectional view, along a line 30-30 of
FIG. 29.

[0042]FIG. 31 is a schematic, cross-sectional view, along a line 31-31 of
FIG. 29.

[0043]FIG. 31a is a schematic, cross-sectional view of other embodiment of
a hollow heater having a carbon nanotube structure.

[0044]FIG. 32 is an isotropic view of other embodiments of a hollow heater
having a carbon nanotube structure.

[0045]FIG. 33 is a schematic, cross-sectional view, along a line 33-33 of
FIG. 32.

[0046]FIG. 34 is an isotropic view of one embodiment of a linear heater
having a carbon nanotube structure.

[0047]FIG. 35 is a schematic, cross-sectional view, along a line 35-35 of
FIG. 34.

[0048]FIG. 36 is a schematic, cross-sectional view, along a line 36-36 of
FIG. 35.

[0049]FIG. 37 is an isotropic view of other embodiment of a linear heater
having a carbon nanotube structure.

[0050]FIG. 38 is a flow chart of a method of one embodiment for
fabricating a linear heater.

DETAILED DESCRIPTION

[0051]The disclosure is illustrated by way of example and not by way of
limitation in the figures of the accompanying drawings in which like
references indicate similar elements. It should be noted that references
to "an" or "one" embodiment in this disclosure are not necessarily to the
same embodiment, and such references mean at least one.

[0052]The present disclose presents several illustrative embodiments of
the heater. The heaters of these illustrative embodiments are generally
divided into three types: planar heater, hollow heater and linear heater.

Planar Heater

[0053]Referring to FIGS. 1 and 2, a planar heater 10 of one embodiment is
shown. The planar heater 10 includes a planar supporter 18, a
heat-reflecting layer 17, a heating element 16, a first electrode 12, a
second electrode 14, and a protecting layer 15. Two wires 19 are
connected to the first and second electrodes 12, 14 to supply a power to
the planar heater 10. The heat-reflecting layer 17 is disposed on a top
surface of the planar supporter 18. The heating element 16 is disposed on
a top surface of the heat-reflecting layer 17. The first electrode 12 and
the second electrode 14 are located within the heating element 16 and
electrically connected to the heating element 16. The protecting layer 15
is disposed on a top surface of the heating element 16. In other
embodiments, the first electrode 12 and the second electrode 14 are
located on a top surface of the heating element 16 and spaced apart from
each other.

[0054]The planar supporter 18 is configured to support the heating element
16 and the heat-reflecting layer 17. The planar supporter 18 is made of
flexible materials or rigid materials. The flexible materials may be
plastics, resins or fibers. The rigid materials may be ceramics, glasses,
or quartzes. When the flexible materials are used, the planar heater 10
can be bent to desired shape according to practical needs. The shape and
size of the planar supporter 18 can be determined according to practical
needs. For example, the planar supporter 18 may be square, round or
triangular. In one embodiment, the planar supporter 18 is a square
ceramic sheet about 1 millimeter (mm) thick. It should be noted that the
planar supporter 18 is optional. The heating element 16 can be a free
standing structure without the need of support from the planar supporter
18.

[0055]The heat-reflecting layer 17 is configured to reflect back the heat
emitted by the heating element 16, and configured for controlling the
direction of the heat emitted by the heating element 16 for single-side
heating. The heat-reflecting layer 17 may be made of insulative
materials. The material of the heat-reflecting layer 17 can be selected
from metal oxides, metal salts, or ceramics. In one embodiment, the
heat-reflecting layer 17 is an aluminum oxide (Al2O3) film. The
thickness of the heat-reflecting layer 17 can be in a range from about
100 micrometer (μm) to about 0.5 mm. In one embodiment, the thickness
of the heat-reflecting layer 17 is about 0.1 mm. The heat-reflecting
layer 17 can be sandwiched between the heating element 16 and the planar
supporter 18. Alternatively, the heat-reflecting layer 17 can be omitted,
and the heating element 16 can be located directly on the planar
supporter 18 if desired. In other embodiments, the heating element 16 can
be free standing without being attached to either a planar supporter 18
or a heat-reflecting layer 17. When there is no heat-reflecting layer,
the planar heater 10 can be used for double-side heating as shown in FIG.
16.

[0056]With reference primarily to FIG. 2, the heating element 16 can be a
carbon nanotube composite structure. The carbon nanotube composite
structure includes a matrix 162 and one or more carbon nanotube
structures 164. The matrix 162 encloses the entire carbon nanotube
structure 164 therein. Alternatively, the carbon nanotube structure 164
includes a plurality of micropores and the matrix 162 is dispersed or
permeated in the micropores of the carbon nanotube structure 164. The
heating element 16 can be a layer-shape structure such as planar or have
a camber. In one embodiment shown in FIGS. 1-2, the heating element 16 is
a rectangular plate with the carbon nanotube structure 164 entirely
enclosed within the matrix 162.

[0057]The carbon nanotube structure 164 can be a free-standing structure,
that is, the carbon nanotube structure 164 can be supported by itself and
does not need a substrate to lay on and supported thereby. When someone
holding at least a point of the carbon nanotube structure, the entire
carbon nanotube structure can be lift without destroyed. The carbon
nanotube structure 164 includes a plurality of carbon nanotubes combined
by van der Waals attractive force therebetween. The carbon nanotube
structure 164 can be a substantially pure structure of the carbon
nanotubes, with few impurities. The carbon nanotubes can be used to form
many different structures and provide a large specific surface area. The
heat capacity per unit area of the carbon nanotube structure 164 can be
less than 2×10-4 J/m2*K. In one embodiment, the heat
capacity per unit area of the carbon nanotube structure 164 is less than
or equal to 1.7×10-6 J/m2*K. As the heat capacity of the
carbon nanotube structure 164 is very low, and the temperature of the
heating element 16 can rise and fall quickly, which makes the heating
element 16 have a high heating efficiency and accuracy. As the carbon
nanotube structure 164 can be substantially pure, the carbon nanotubes
are not easily oxidized and the lifespan of the heating element 16 will
be relatively longer. Further, the carbon nanotubes have a low density,
about 1.35 g/cm3, so the heating element 16 is light. As the heat
capacity of the carbon nanotube structure 164 is very low, the heating
element 16 has a high response heating speed. As the carbon nanotube has
large specific surface area, the carbon nanotube structure 164 with a
plurality of carbon nanotubes has large specific surface area. When the
specific surface of the carbon nanotube structure 164 is large enough,
the carbon nanotube structure 164 is adhesive and can be directly applied
to a surface.

[0058]The carbon nanotubes in the carbon nanotube structure 164 can be
arranged orderly or disorderly. The term `disordered carbon nanotube
structure` refers to a structure where the carbon nanotubes are arranged
along different directions, and the aligning directions of the carbon
nanotubes are random. The number of the carbon nanotubes arranged along
each different direction can be almost the same (e.g. uniformly
disordered). The disordered carbon nanotube structure can be isotropic,
namely the carbon nanotube film has properties identical in all
directions of the carbon nanotube film. The carbon nanotubes in the
disordered carbon nanotube structure can be entangled with each other.

[0059]The carbon nanotube structure 164 including ordered carbon nanotubes
is an ordered carbon nanotube structure. The term `ordered carbon
nanotube structure` refers to a structure where the carbon nanotubes are
arranged in a consistently systematic manner, e.g., the carbon nanotubes
are arranged approximately along a same direction and/or have two or more
sections within each of which the carbon nanotubes are arranged
approximately along a same direction (different sections can have
different directions). The carbon nanotubes in the carbon nanotube
structure 164 can be selected from single-walled, double-walled, and/or
multi-walled carbon nanotubes.

[0060]The carbon nanotube structure 164 can be a carbon nanotube film
structure with a thickness ranging from about 0.5 nanometers (nm) to
about 1 mm. The carbon nanotube film structure can include at least one
carbon nanotube film. The carbon nanotube structure 164 can also be at
least one linear carbon nanotube structure with a diameter ranging from
about 0.5 nm to about 1 mm. The carbon nanotube structure 164 can also be
a combination of the carbon nanotube film structure and the linear carbon
nanotube structure. It is understood that any carbon nanotube structure
164 described can be used with all embodiments. It is also understood
that any carbon nanotube structure 164 may or may not employ a support
structure.

[0061]Carbon Nanotube Film Structure

[0062]In one embodiment, the carbon nanotube film structure includes at
least one drawn carbon nanotube film. A film can be drawn from a carbon
nanotube array, to obtain a drawn carbon nanotube film. Examples of drawn
carbon nanotube film are taught by U.S. Pat. No. 7,045,108 to Jiang et
al., and WO 2007015710 to Zhang et al. The drawn carbon nanotube film
includes a plurality of successive and oriented carbon nanotubes joined
end-to-end by van der Waals attractive force therebetween. The drawn
carbon nanotube film is a free-standing film. Referring to FIGS. 3 to 4,
each drawn carbon nanotube film includes a plurality of successively
oriented carbon nanotube segments 143 joined end-to-end by van der Waals
attractive force therebetween. Each carbon nanotube segment 143 includes
a plurality of carbon nanotubes 145 parallel to each other, and combined
by van der Waals attractive force therebetween. As can be seen in FIG. 3,
some variations can occur in the drawn carbon nanotube film. The carbon
nanotubes 145 in the drawn carbon nanotube film are oriented along a
preferred orientation. The carbon nanotube film can be treated with an
organic solvent to increase the mechanical strength and toughness of the
carbon nanotube film and reduce the coefficient of friction of the carbon
nanotube film. The thickness of the carbon nanotube film can range from
about 0.5 nm to about 100 μm.

[0063]The carbon nanotube film structure of the heating element 16 can
include at least two stacked carbon nanotube films. In other embodiments,
the carbon nanotube structure can include two or more coplanar carbon
nanotube films, and can include layers of coplanar carbon nanotube films.
Additionally, when the carbon nanotubes in the carbon nanotube film are
aligned along one preferred orientation (e.g., the drawn carbon nanotube
film), an angle can exist between the orientations of carbon nanotubes in
adjacent films, whether stacked or adjacent. Adjacent carbon nanotube
films can be combined by only the van der Waals attractive force
therebetween. The number of the layers of the carbon nanotube films is
not limited. However, the thicker the carbon nanotube structure, the
specific surface area will decrease. An angle between the aligned
directions of the carbon nanotubes in two adjacent carbon nanotube films
can range from about 0 degrees to about 90 degrees. When the angle
between the aligned directions of the carbon nanotubes in adjacent carbon
nanotube films is larger than 0 degrees, a microporous structure is
defined by the carbon nanotubes in the heating element 16. The carbon
nanotube structure in an embodiment employing these films will have a
plurality of micropores. Stacking the carbon nanotube films will also add
to the structural integrity of the carbon nanotube structure.

[0064]In other embodiments, the carbon nanotube film structure includes a
flocculated carbon nanotube film. Referring to FIG. 5, the flocculated
carbon nanotube film can include a plurality of long, curved, disordered
carbon nanotubes entangled with each other. Further, the flocculated
carbon nanotube film can be isotropic. The carbon nanotubes can be
substantially uniformly dispersed in the carbon nanotube film. Adjacent
carbon nanotubes are acted upon by van der Waals attractive force to
obtain an entangled structure with micropores defined therein. It is
understood that the flocculated carbon nanotube film is very porous.
Sizes of the micropores can be less than 10 μm. The porous nature of
the flocculated carbon nanotube film will increase specific surface area
of the carbon nanotube structure. Further, due to the carbon nanotubes in
the carbon nanotube structure being entangled with each other, the carbon
nanotube structure employing the flocculated carbon nanotube film has
excellent durability, and can be fashioned into desired shapes with a low
risk to the integrity of the carbon nanotube structure. The flocculated
carbon nanotube film, in some embodiments, will not require the use of
the planar supporter 18 due to the carbon nanotubes being entangled and
adhered together by van der Waals attractive force therebetween. The
thickness of the flocculated carbon nanotube film can range from about
0.5 nm to about 1 mm.

[0065]In other embodiments, the carbon nanotube film structure can include
at least a pressed carbon nanotube film. Referring to FIG. 6, the pressed
carbon nanotube film can be a free-standing carbon nanotube film. The
carbon nanotubes in the pressed carbon nanotube film are arranged along a
same direction or along different directions. The carbon nanotubes in the
pressed carbon nanotube film can rest upon each other. Adjacent carbon
nanotubes are attracted to each other and combined by van der Waals
attractive force. An angle between a primary alignment direction of the
carbon nanotubes and a surface of the pressed carbon nanotube film is
about 0 degrees to approximately 15 degrees. The greater the pressure
applied, the smaller the angle obtained. When the carbon nanotubes in the
pressed carbon nanotube film are arranged along different directions, the
carbon nanotube structure can be isotropic. Here, "isotropic" means the
carbon nanotube film has properties identical in all directions parallel
to a surface of the carbon nanotube film. The thickness of the pressed
carbon nanotube film ranges from about 0.5 nm to about 1 mm. Examples of
pressed carbon nanotube film are taught by US PGPub. 20080299031A1 to Liu
et al.

[0068]The carbon nanotube wire can be untwisted or twisted. Treating the
drawn carbon nanotube film with a volatile organic solvent can obtain the
untwisted carbon nanotube wire. In one embodiment, the organic solvent is
applied to soak the entire surface of the drawn carbon nanotube film.
During the soaking, adjacent parallel carbon nanotubes in the drawn
carbon nanotube film will bundle together, due to the surface tension of
the organic solvent as it volatilizes, and thus, the drawn carbon
nanotube film will be shrunk into an untwisted carbon nanotube wire.
Referring to FIG. 7, the untwisted carbon nanotube wire includes a
plurality of carbon nanotubes substantially oriented along a same
direction (i.e., a direction along the length direction of the untwisted
carbon nanotube wire). The carbon nanotubes are parallel to the axis of
the untwisted carbon nanotube wire. In one embodiment, the untwisted
carbon nanotube wire includes a plurality of successive carbon nanotube
segments joined end to end by van der Waals attractive force
therebetween. Each carbon nanotube segment includes a plurality of carbon
nanotubes substantially parallel to each other, and combined by van der
Waals attractive force therebetween. The carbon nanotube segments can
vary in width, thickness, uniformity and shape. Length of the untwisted
carbon nanotube wire can be arbitrarily set as desired. A diameter of the
untwisted carbon nanotube wire ranges from about 0.5 nm to about 100
μm.

[0069]The twisted carbon nanotube wire can be obtained by twisting a drawn
carbon nanotube film using a mechanical force to turn the two ends of the
drawn carbon nanotube film in opposite directions. Referring to FIG. 8,
the twisted carbon nanotube wire includes a plurality of carbon nanotubes
helically oriented around an axial direction of the twisted carbon
nanotube wire. In one embodiment, the twisted carbon nanotube wire
includes a plurality of successive carbon nanotube segments joined end to
end by van der Waals attractive force therebetween. Each carbon nanotube
segment includes a plurality of carbon nanotubes substantially parallel
to each other, and combined by van der Waals attractive force
therebetween. Length of the carbon nanotube wire can be set as desired. A
diameter of the twisted carbon nanotube wire can be from about 0.5 nm to
about 100 μm. Further, the twisted carbon nanotube wire can be treated
with a volatile organic solvent after being twisted. After being soaked
by the organic solvent, the adjacent paralleled carbon nanotubes in the
twisted carbon nanotube wire will bundle together, due to the surface
tension of the organic solvent when the organic solvent volatilizing. The
specific surface area of the twisted carbon nanotube wire will decrease,
while the density and strength of the twisted carbon nanotube wire will
be increased.

[0070]The linear carbon nanotube structure can include one or more carbon
nanotube wires. The carbon nanotube wires in the linear carbon nanotube
structure can be, twisted and/or untwisted. Referring to FIG. 9, in an
untwisted linear carbon nanotube structure 1642a, the carbon nanotube
wires 1644 are parallel with each other, and the axes of the nanotube
wires 1644 extend along a same direction. Referring to FIG. 10, in a
twisted linear carbon nanotube structure 1642b, carbon nanotube wires
1644 are twisted with each other.

[0071]The matrix 162 can be made of a material being selected from
polymer, inorganic non-metal or combinations thereof. The material or the
precursor of the matrix 162 can be liquid or gas at a certain temperature
so that the material or the precursor of the matrix 162 can infiltrate
into the micropores of the carbon nanotube structure 164 during the
process of making the heating element 16. The matrix 162 has good thermal
stability and is not easy to be distorted, melted and decomposed under
the working temperature of the planar heater 10.

[0074]The layer-shaped carbon nanotube composite structure can include a
matrix and a layer-shaped carbon nanotube structure having a plurality of
micropores. In one example, the matrix is dispersed in the micropores of
the layer-shaped carbon nanotube structure. In another example, the
layer-shaped carbon nanotube structure is enclosed within in a
layer-shape matrix. The layer-shaped carbon nanotube structure can be a
plurality of carbon nanotube film structure stacked with each other. When
the layer-shaped carbon nanotube structure includes a single linear
carbon nanotube structure 1642, the single linear carbon nanotube
structure 1642 can be folded to obtain a layer-shape structure as shown
in FIG. 11. When the layer-shaped carbon nanotube structure includes a
plurality of linear carbon nanotube structures 1642, the linear carbon
nanotube structures 1642 can be paralleled with each other (not shown),
crossed with each other as shown in FIG. 12 or weaved together as shown
in FIG. 13 to obtain a layer-shape structure.

[0075]The linear carbon nanotube composite structure can include a matrix
and a linear carbon nanotube structure having a plurality of micropores.
In one example, the linear carbon nanotube structure is enclosed within
the linear matrix. In another example, the matrix is dispersed in the
micropores of the linear carbon nanotube structure. A single linear
carbon nanotube composite structure can be folded to obtain a layer-shape
heating element 16. A plurality of linear carbon nanotube composite
structures can be paralleled with each other, crossed with each other or
weaved together to obtain a layer-shape heating element 16.

[0076]Referring to FIG. 14, the heating element 16 can include a plurality
of planar carbon nanotube structures 164 separately located in the matrix
162. The planar carbon nanotube structures 164 are parallel arranged
between the first electrode 12 and the second electrode 14. This
structure allows the heating element 16 to have different heating
temperature in different locations. Furthermore, this structure lower the
amount of carbon nanotubes used in fabricating the heating element 16.

[0077]In one embodiment, a heating element 16, comprising drawn carbon
nanotube film and epoxy resin, is broken by pulling along the aligned
directions of the carbon nanotubes. Referring to FIG. 15, it shows an
enlarged view of a fracture surface of the heating element and shows that
the carbon nanotubes in heating element are still oriented along a
preferred orientation after forming a carbon nanotube composite structure
with epoxy resin. Then, the first electrode 12 and the second electrode
14 are attached to the broken position and electrically connected to the
drawn carbon nanotube film in the epoxy resin matrix after tearing.

[0078]The matrix 162 in the micropores of the carbon nanotube structure
164 can combine the carbon nanotubes of the carbon nanotube structure 164
and prevent the carbon nanotubes from separating. When the entire carbon
nanotube structure 164 is enclosed within the matrix 162, the matrix 162
can protect the carbon nanotube structure 164 from outside contaminants.
When the material of the matrix 162 is insulative, the matrix 162 can
electrically insulate the carbon nanotube structure 164 from the external
environment. The matrix 162 allows the heat in the heating element 16 to
be dispersed uniformly. The matrix 162 can further slow down the
temperature changing speed of the heating element 16. When the matrix 162
is made of flexible polymer, the flexibility of the heating element 16
can be improved.

[0079]The heating element 16 can be fabricated by combining the free
standing carbon nanotube structure 164 with the matrix 162 directly.
Because the carbon nanotubes can be uniformly dispersed in the matrix 162
and form a free standing structure, the weight percentage of the carbon
nanotubes in the heating element 16 can be as high 99% in the composite
structure. The greater the weight percentage of the carbon nanotubes in
the heating element 16, the greater the heating temperature for a given
voltage. Furthermore, the heating element 16 can have different heating
temperature and response time by controlling the weight percentage of the
carbon nanotubes for a given voltage. In one embodiment, the weight
percentage of the carbon nanotubes in the heating element 16 can range
from about 0.1% to about 5%. In other embodiments, the weight percentage
of the carbon nanotubes in the heating element 16 can range from about 5%
to about 10%. In other embodiments, the weight percentage of the carbon
nanotubes in the heating element 16 can range from about 10% to about
30%. In other embodiments, the weight percentage of the carbon nanotubes
in the heating element 16 can range from about 30% to about 90%.

[0080]The first electrode 12 and the second electrode 14 are electrically
connected to the heating element 16. Furthermore, it is imperative that
the first electrode 12 can be separated from the second electrode 14 to
prevent short circuit of the two electrodes 12, 14.

[0081]When the matrix 162 is dispersed in the micropores of the carbon
nanotube structure 164, parts of the carbon nanotube structure 164 can be
exposed. The first electrode 12 and the second electrode 14 can be
disposed on same surface or opposite surfaces of the heating element 16
to have contact with the carbon nanotube structure 164. The first
electrode 12 and the second electrode 14 can be directly electrically
attached to the heating element 16 by, for example, a conductive adhesive
(not shown), such as silver adhesive. Because, some of the carbon
nanotube structures have large specific surface area and are adhesive in
nature, in some embodiments, the first electrode 12 and the second
electrode 14 can be adhered directly to heating element 16. It should be
noted that any other bonding ways may be adopted as long as the first
electrode 12 and the second electrode 14 are electrically connected to
the heating element 16. When the entire carbon nanotube structure 164 is
enclosed within the matrix 162 as shown in FIG. 2, the first electrode 12
and the second electrode 14 can also be in the matrix 162 and make
contact with the carbon nanotube structure 164. The first electrode 12
and the second electrode 14 can be electrically connected to two wires
19, which extend through outside of the matrix 162.

[0082]The shape of the first electrode 12 or the second electrode 14 is
not limited and can be lamellar, rod, wire, and block among other shapes.
In one embodiment shown in FIG. 1, the first electrode 12 and the second
electrode 14 are both lamellar and parallel with each other. The material
of the first electrode 12 and the second electrode 14 can be selected
from metals, conductive resins, or any other suitable materials. In some
embodiments, the carbon nanotubes in the heating element 16 are aligned
along a direction from the first electrode 12 to the second electrode 14.
In other embodiments, at least one of the first electrode 12 and the
second electrode 14 includes at least a carbon nanotube film or at least
a linear carbon nanotube structure. In one embodiment, each of the first
electrode 12 and the second electrode 14 includes a linear carbon
nanotube structure. The linear carbon nanotube structures are separately
disposed on the two ends of the heating element 16.

[0083]The protecting layer 15 is disposed on a surface of the heating
element 16. In one embodiment, the protecting layer 15 fully covers a top
surface of the heating element 16. The protecting layer 15 and the
heat-reflecting layer 17 are located at two opposite flanks of the
heating element 16. The material of protecting layer 15 can be
electrically conductive or insulative. The electrically conductive
material can be metal or alloy. The insulative material can be resin,
plastic or rubber. The thickness of the protecting layer 15 can range
from about 0.5 μm to about 2 mm. When the material of the protecting
layer 15 is insulative, the protecting layer 15 can electrically and/or
thermally insulate the planar heater 10 from the external environment.
The protecting layer 15 can also protect the heating element 16 including
the carbon nanotube structure having an exposed portion from outside
contaminants. The protecting layer 15 is an optional structure and can be
omitted.

[0084]Referring to FIG. 16, in other embodiments, the planar heater 10 can
have only a heating element 16, a first electrode 12 and a second
electrode 14. The heating element 16 includes a matrix 162 and a carbon
nanotube structure 164 enclosed therein. The first electrode 12 and the
second electrode 14 are electrically connected to the carbon nanotube
structure 164 and enclosed in the matrix 162. The matrix 162 contains the
carbon nanotube structure 164, the first electrode 12 and the second
electrode 14 therein. The carbon nanotube structure 164 extends from the
first electrode 12 to the second electrode 14.

[0085]In use, when a voltage is applied to the first electrode 12 and the
second electrode 14 of the planar heater 10, the carbon nanotube
structure of the heating element 16 radiates heat at a certain
wavelength. The object to be heated can be directly positioned on the
planar heater 10 or kept away from the planar heater 10. By controlling
the specific surface area of the carbon nanotube structure 164, selecting
the voltage and the thickness of the carbon nanotube structure 164, the
heating element 16 emits heat at different wavelengths. If the voltage is
determined at a certain value, the wavelength of the electromagnetic
waves emitted from the carbon nanotube structure 164 is inversely
proportional to the thickness of the carbon nanotube structure 164. That
is to say, the greater the thickness of carbon nanotube structure 164 is,
the shorter the wavelength of the electromagnetic waves is. Further, if
the thickness of the carbon nanotube structure 164 is determined at a
certain value, the greater the voltage applied to the electrodes, the
shorter the wavelength of the electromagnetic waves. As such, the planar
heater 10 can easily be controlled for emitting a visible light and
create general thermal radiation or emit infrared radiation.

[0086]Further, due to carbon nanotubes having an ideal black body
structure, the carbon nanotube structure 164 has excellent electrical
conductivity, thermal stability, and high thermal radiation efficiency.
The planar heater 10 can be safely exposed, while working, to oxidizing
gases in a typical environment. The planar heater 10 can radiate an
electromagnetic wave with a long wavelength when a voltage is applied on
the planar heater 10. The radiating efficiency is relatively high.

[0087]The voltage applied to the planar heater 10 depends on the material
of the matrix 162 and the weight percentage of the carbon nanotubes so
that the heating temperature of the planar heater 10 is below the melting
point of the matrix 162. In one embodiment, the material of the matrix
162 is polymer and the weight percentage of the carbon nanotubes in the
heating element 16 range from about 0.1% to about 5%, the voltage
supplied to the planar heater 10 can range from about 0 volts to about 10
volts, and the heating temperature of the planar heater 10 is below
120° C. In other embodiments, the material of the matrix 162 is
ceramic and the weight percentage of the carbon nanotubes in the heating
element 16 range from about 0.1% to about 5%, the voltage supplied to the
planar heater 10 can range from about 10 volts to about 30 volts and the
heating temperature of the planar heater 10 can range from about
120° C. to about 500° C. In one embodiment, a planar heater
10 is tested. The planar heater 10 has a heating element 16 including an
epoxy resin matrix and one hundred layers of drawn carbon nanotube films
stacked on each other and dispersed therein. The heating element 16 is a
square having a thickness of about 300 μm and a length of about 1 cm.
The weight percentage of the carbon nanotubes in the heating element 16
is about 1%. Referring to FIG. 17, the higher the voltage supplied to the
planar heater 10, the faster the temperature of the planar heater 10
rise. Thus, the planar heater 10 can be used in electric heaters,
infrared therapy devices, electric radiators, and other related devices.

[0088]Referring FIG. 18, an embodiment of a method for making the planar
heater 10 includes the steps of: [0089]S1: making a carbon nanotube
structure 164 having a plurality of micropores; [0090]S2: connecting a
first electrode 12 and a second electrode 14 to the carbon nanotube
structure 164; [0091]S3: fixing the carbon nanotube structure 164 on a
surface of a planar supporter 18; and [0092]S4: supply a material into
the carbon nanotube structure 164 to achieve a carbon nanotube composite.

[0093]It is to be understood that, before step S4, an additional step of
applying a heat-reflecting layer 17 to a surface of the planar supporter
18 can be performed. The heat-reflecting layer will then be located
between the planar supporter 18 and the carbon nanotube structure 164.
The heat-reflecting layer 17 can be created by coating method, chemical
deposition method, ion sputtering method, and so on. In one embodiment,
the heat-reflecting layer 17 is a film made of aluminum oxide. The
heat-reflecting layer 17 can be coated on the carbon nanotube structure
164. After step S4, an additional step of applying a protecting layer 15
to cover the carbon nanotube structure 164 can be performed. The
protecting layer 15 can be applied by a sputtering method or a coating
method.

[0095]In step S1, a method of making a drawn carbon nanotube film includes
the steps of [0096]S11: providing an array of carbon nanotubes; and
[0097]S12: pulling out at least a drawn carbon nanotube film from the
carbon nanotube array.

[0098]In step S11, a method of making the array of carbon nanotubes
includes: [0099]S111: providing a substantially flat and smooth
substrate; [0100]S112: applying a catalyst layer on the substrate;
[0101]S113: annealing the substrate with the catalyst at a temperature in
the approximate range of 700° C. to 900° C. in air for
about 30 to 90 minutes; [0102]S114: heating the substrate with the
catalyst at a temperature in the approximate range from 500° C. to
740° C. in a furnace with a protective gas therein; and
[0103]S115: supplying a carbon source gas to the furnace for about 5 to
30 minutes and growing a super-aligned array of the carbon nanotubes from
the substrate.

[0104]In step S111, the substrate can be a P or N-type silicon wafer.
Quite suitably, a 4-inch P-type silicon wafer is used as the substrate.

[0105]In step S112, the catalyst can be made of iron (Fe), cobalt (Co),
nickel (Ni), or any combination alloy thereof.

[0106]In step S114, the protective gas can be made up of at least one of
nitrogen (N2), ammonia (NH3), and a noble gas.

[0107]In step S115, the carbon source gas can be a hydrocarbon gas, such
as ethylene (C2H4), methane (CH4), acetylene
(C2H2), ethane (C2H6), or any combination thereof.

[0108]In step S12, a drawn carbon nanotube film can be fabricated by the
steps of: [0109]S121: selecting one or more carbon nanotubes having a
predetermined width from the array of carbon nanotubes; and [0110]S122:
pulling the carbon nanotubes to obtain nanotube segments at an
even/uniform speed to achieve a uniform carbon nanotube film.

[0111]In step S121, the carbon nanotube segment includes a plurality of
parallel carbon nanotubes. The carbon nanotube segments can be selected
by using an adhesive tape as the tool to contact the super-aligned array
of carbon nanotubes. In step S122, the pulling direction is substantially
perpendicular to the growing direction of the super-aligned array of
carbon nanotubes.

[0112]More specifically, during the pulling process, as the initial carbon
nanotube segments are drawn out, other carbon nanotube segments are also
drawn out end to end due to van der Waals attractive force between ends
of adjacent segments. This process of pulling produces a substantially
continuous and uniform carbon nanotube film having a predetermined width
can be obtained.

[0113]After the step of S12, the drawn carbon nanotube film can be treated
by applying organic solvent to the drawn carbon nanotube film to soak the
entire surface of the carbon nanotube film. The organic solvent is
volatile and can be selected from ethanol, methanol, acetone,
dichloromethane, chloroform, or any appropriate mixture thereof. In the
one embodiment, the organic solvent is ethanol. After being soaked by the
organic solvent, adjacent carbon nanotubes in the carbon nanotube film
that are able to do so, bundle together, due to the surface tension of
the organic solvent when the organic solvent is volatilizing. In another
aspect, due to the decrease of the specific surface area via bundling,
the mechanical strength and toughness of the drawn carbon nanotube film
are increased and the coefficient of friction of the carbon nanotube
films is reduced. Macroscopically, the drawn carbon nanotube film will be
an approximately uniform film.

[0114]The width of the drawn carbon nanotube film depends on a size of the
carbon nanotube array. The length of the drawn carbon nanotube film can
be set as desired. In one embodiment, when the substrate is a 4 inch type
wafer, a width of the carbon nanotube film can be in an approximate range
from 1 centimeter (cm) to 10 cm, the length of the carbon nanotube film
can reach to about 120 m, the thickness of the drawn carbon nanotube film
can be in an approximate range from 0.5 nm to 100 microns. Multiple films
can be adhered together to obtain a film of any desired size.

[0115]In step S1, a method of making the pressed carbon nanotube film
includes the following steps: [0116]S11': providing a carbon nanotube
array and a pressing device; and [0117]S12': pressing the array of carbon
nanotubes to obtain a pressed carbon nanotube film.

[0118]In step S11', the carbon nanotube array can be made by the same
method as S11.

[0119]In the step S12', a certain pressure can be applied to the array of
carbon nanotubes by the pressing device. In the process of pressing, the
carbon nanotubes in the array of carbon nanotubes separate from the
substrate and obtain the carbon nanotube film under pressure. The carbon
nanotubes are substantially parallel to a surface of the carbon nanotube
film.

[0120]In one embodiment, the pressing device can be a pressure head. The
pressure head has a smooth surface. It is to be understood that, the
shape of the pressure head and the pressing direction can determine the
direction of the carbon nanotubes arranged therein. When a pressure head
(e.g. a roller) is used to travel across and press the array of carbon
nanotubes along a predetermined single direction, a carbon nanotube film
having a plurality of carbon nanotubes primarily aligned along a same
direction is obtained. It can be understood that there may be some
variation in the film. Different alignments can be achieved by applying
the roller in different directions over an array. Variations on the film
can also occur when the pressure head is used to travel across and press
the array of carbon nanotubes several of times, variation will occur in
the orientation of the nanotubes. Variations in pressure can also achieve
different angles between the carbon nanotubes and the surface of the
semiconducting layer on the same film. When a planar pressure head is
used to press the array of carbon nanotubes along the direction
perpendicular to the substrate, a carbon nanotube film having a plurality
of carbon nanotubes isotropically arranged can be obtained. When a
roller-shaped pressure head is used to press the array of carbon
nanotubes along a certain direction, a carbon nanotube film having a
plurality of carbon nanotubes aligned along the certain direction is
obtained. When a roller-shaped pressure head is used to press the array
of carbon nanotubes along different directions, a carbon nanotube film
having a plurality of sections having carbon nanotubes aligned along
different directions is obtained.

[0121]In step S1, the flocculated carbon nanotube film can be made by the
following method: [0122]S11'': providing a carbon nanotube array;
[0123]S12'': separating the array of carbon nanotubes from the substrate
to get a plurality of carbon nanotubes; [0124]S13'': adding the plurality
of carbon nanotubes to a solvent to get a carbon nanotube floccule
structure in the solvent; and [0125]S14'': separating the carbon nanotube
floccule structure from the solvent, and shaping the separated carbon
nanotube floccule structure into a carbon nanotube film to achieve a
flocculated carbon nanotube film.

[0126]In step S11'', the carbon nanotube array can be fabricated by the
same method as step (a1).

[0127]In step S12'', the array of carbon nanotubes is scraped off the
substrate to obtain a plurality of carbon nanotubes. The length of the
carbon nanotubes can be above 10 microns.

[0128]In step S13'', the solvent can be selected from water or volatile
organic solvent. After adding the plurality of carbon nanotubes to the
solvent, a process of flocculating the carbon nanotubes can, suitably, be
executed to create the carbon nanotube floccule structure. The process of
flocculating the carbon nanotubes can be selected from ultrasonic
dispersion of the carbon nanotubes or agitating the carbon nanotubes. In
one embodiment ultrasonic dispersion is used to flocculate the solvent
containing the carbon nanotubes for about 10-30 minutes. Due to the
carbon nanotubes in the solvent having a large specific surface area and
the tangled carbon nanotubes having a large van der Waals attractive
force, the flocculated and tangled carbon nanotubes obtain a network
structure (e.g., floccule structure).

[0129]In step S14'', the process of separating the floccule structure from
the solvent includes the substeps of: [0130]S14''1: filtering out the
solvent to obtain the carbon nanotube floccule structure; and
[0131]S14''2: drying the carbon nanotube floccule structure to obtain the
separated carbon nanotube floccule structure.

[0132]In step S14''1, the carbon nanotube floccule structure can be
disposed in room temperature for a period of time to dry the organic
solvent therein. The time of drying can be selected according to
practical needs. The carbon nanotubes in the carbon nanotube floccule
structure are tangled together.

[0133]In step S14''2, the process of shaping includes the substeps of:
[0134]S14''21: putting the separated carbon nanotube floccule structure
into a container (not shown), and spreading the carbon nanotube floccule
structure to obtain a predetermined structure; [0135]S14''22: pressing
the spread carbon nanotube floccule structure with a certain pressure to
yield a desirable shape; and [0136]S14''23: removing the residual solvent
contained in the spread floccule structure to obtain the flocculated
carbon nanotube film.

[0137]Through the flocculating, the carbon nanotubes are tangled together
by van der

[0138]Walls attractive force to obtain a network structure/floccule
structure. Thus, the flocculated carbon nanotube film has good tensile
strength. The flocculated carbon nanotube film includes a plurality of
micropores defined by the disordered carbon nanotubes. A diameter of the
micropores can be less than about 100 micron. As such, a specific area of
the flocculated carbon nanotube film is extremely large. Additionally,
the pressed carbon nanotube film is essentially free of a binder and
includes a large amount of micropores. The method for making the
flocculated carbon nanotube film is simple and can be used in mass
production.

[0139]In step S1, a linear carbon nanotube structure includes carbon
nanotube wires and/or linear carbon nanotube structures. The carbon
nanotube wire can be made by the following steps: [0140]S11''': making
a drawn carbon nanotube film; and [0141]S12''': treating the drawn carbon
nanotube film to obtain a carbon nanotube wire.

[0142]In step S11''', the method for making the drawn carbon nanotube film
is the same the step S11.

[0143]In step S12''', the drawn carbon nanotube film is treated with an
organic solvent to obtain an untwisted carbon nanotube wire or is twisted
by a mechanical force (e.g., a conventional spinning process) to obtain a
twist carbon nanotube wire. The organic solvent is volatilizable and can
be selected from ethanol, methanol, acetone, dichloroethane, or
chloroform. After soaking in the organic solvent, the carbon nanotube
segments in the carbon nanotube film can at least partially bundle into
the untwisted carbon nanotube wire due to the surface tension of the
organic solvent.

[0144]It is to be understood that a narrow carbon nanotube film can serve
as a wire. In this situation, through microscopically view, the carbon
nanotube structure 164 is a flat film, and through macroscopically view,
the narrow carbon nanotube film would look like a long wire.

[0145]In step S1, the linear carbon nanotube structure can be made by
bundling two or more carbon nanotube wires together. The linear carbon
nanotube structure can be twisted or untwisted. In the untwisted linear
carbon nanotube structure, the carbon nanotube wires are parallel with
each other, and the carbon nanotubes can be kept together by an adhesive
(not shown). In the twisted linear carbon nanotube structure, the carbon
nanotube wires twisted with each other, and can be adhered together by an
adhesive or a mechanical force.

[0146]In step S1, the drawn carbon nanotube film, the pressed carbon
nanotube film, the flocculated carbon nanotube film, or the linear carbon
nanotube structure can be overlapped, stacked with each other, and/or
disposed side by side to make a carbon nanotube structure 164. It is also
understood that this carbon nanotube structure 164 can be employed by all
embodiments.

[0147]In step S2, the first electrode 12 and the second electrode 14 are
made of conductive materials, and applied on the surface of the carbon
nanotube structure 164 by sputtering method or coating method. The first
electrode 12 and the second electrode 14 can also be attached on the
carbon nanotube structure 164 directly with a conductive adhesive or by a
mechanical force. Further, silver paste can be applied on the surface of
the carbon nanotube structure 164 directly to obtain the first electrode
12 and the second electrode 14.

[0148]In step S3, the carbon nanotube structure 164 can be fixed on the
surface of the planar supporter 18 by an adhesive. The carbon nanotube
structure 164 can be fixed on the surface of the planar supporter by a
mechanical method, such as bolt, splint.

[0149]In the step S4, the material can be a polymer material or an
inorganic nonmetal material. The polymer material or the nonmetal
material can be applied in a liquid state, in a gaseous state or in a
slurry state. The liquid state or slurry state material is hardenable.
The polymer material can be thermoplastic polymer or thermosetting
polymer. The thermosetting material can be selected from epoxy resin,
bismaleimide resin, cyanate ester resin, or silicone rubber. The
thermoplastic material can be selected from polypropylene, polyethylene,
polyvinyl alcohol, or polymethacrylate resin. The inorganic nonmetal
material can be selected from glass, ceramic or semiconductor. The
inorganic nonmetal material can be in a slurry state or in a gaseous
state. The slurry state inorganic nonmetal material can be obtained by
the following steps: supplying a plurality of inorganic nonmetal material
particles; adding these inorganic nonmetal material particles into a
solvent; mixing round the solvent with the material to form a slurry
state inorganic nonmetal material. The gaseous state inorganic nonmetal
material can be obtained by a method such as sputtering, chemical vapor
deposition (CVD), physical deposition (CVD) or thermal evaporation.

[0150]When the material is applied in the liquid state, the carbon
nanotube structure 164 can be immersed in the liquid state material. When
the material is applied in the gaseous state, the gaseous state material
can be deposited on the carbon nanotube structure 164. When the material
is applied in the slurry state, the slurry can be applied to the carbon
nanotube structure 164 by coating or screen printing.

[0151]In step S4, according to one embodiment, the step of applying the
material into the carbon nanotube structure 164 includes: S41: providing
a die, disposing the carbon nanotube structure 164 in the die; S42:
providing a liquid-state thermosetting polymer; S43: injecting the
liquid-state thermosetting polymer into the die, and thereby immersing
the carbon nanotube film structure in the liquid-state thermosetting
polymer to obtain a carbon nanotube composite preform; and S44:
solidifying the liquid-state thermosetting polymer to achieve a carbon
nanotube composite.

[0152]In step S42, according to one embodiment, a viscosity of the
liquid-state thermosetting polymer is less than 5 pascal-seconds (Pas),
which can be kept at room temperature for at least 30 minutes. The
liquid-state thermosetting polymer includes polymer and at least one
additive. The at least one additive can be selected from solidifying
agent, modifying agent, diluting agent, filler, or any combination
thereof. A mass ratio of the polymer to the additive can range from about
7:3 to about 19:1. The liquid-state thermosetting polymer can be selected
from phenolic resin, epoxy resin, bismaleimide resin, triazine resin,
polyimide, or polymethyl methacrylate. The solidifying agents can be
selected from aliphatic amine, aliphatic cyclic amine, aromatic amine,
polyamide, acid anhydride, tertiary amine, or any combination thereof,
and are ultimately used to accelerate the process of solidifying the
liquid-state thermosetting polymer. The modifying agents can be selected
from polysulphide rubber, polyamide resin, acrylonitrile rubber, or any
combination thereof, and are ultimately used to improve the property of
the liquid-state thermosetting polymer. The diluting agents can be
selected from diglycidyl ether, polyglycidyl ether, butyl epoxy propyl
ether 660, allylphenol, or any combination thereof. The fillers can be
selected from asbestos fiber, glass fiber, quartz powder, aluminum oxide,
or any combination thereof, and are ultimately used to improve the
heat-dissipation of the liquid-state thermosetting polymer.

[0153]In the step of S42, according to one embodiment, the liquid-state
thermosetting polymer can be fabricated by the following substeps: (S421)
providing a polymer in a container, and heating and agitating the polymer
at a temperature of less than 300° C.; (S422) adding at least one
additive into the polymer; and (S423) heating and uniformly agitating the
polymer with the at least one additive at a temperature of less than
300° C., thereby obtaining the liquid-state thermosetting polymer.

[0154]In step S42, according to other embodiments, the method of
fabricating the liquid-state thermosetting polymer includes: (S421')
providing a mixture of epoxy resin of glycidyl ether and epoxy resin of
glycidyl fat disposed in a container, heating the mixture to a
temperature ranging from about 30° C. to about 60° C., and
agitating the mixture for about 10 minutes; (S422') adding aliphatic
amine and diglycidyl ether to the mixture; and (S423') heating the
mixture to a temperature ranging from about 30° C. to about
60° C., and obtaining a liquid-state thermosetting polymer
comprising epoxy resin.

[0155]In the step S43, the lower the viscosity of the liquid-state
thermosetting polymer, the easier liquid-state thermosetting polymer can
permeate into the microporous structure of the carbon nanotube structure
164. In order to make the liquid-state thermosetting polymer better
permeate into the carbon nanotube structure 164 well, the air in the die
can be removed and create a vacuum therein. The pressure in the die can
be kept more than 10 minutes.

[0156]In step S44, the liquid-state thermosetting polymer can be
solidified by the following substeps: S441 heating the carbon nanotube
composite preform to a predetermined temperature and maintaining the
predetermined temperature for no more than 100 hours; and S442 cooling
the carbon nanotube composite preform to room temperature, thereby
obtaining the carbon nanotube composite.

[0157]According to one embodiment, the step S441 includes the following
substeps: S4411 heating the carbon nanotube composite preform to a
temperature ranging from 50° C. to 70° C. for a period of
about 1-3 hours; S4412 heating the carbon nanotube composite preform to a
temperature ranging from 80° C. to 100° C. for a period of
about 1 hour to 3 hours; S4413 heating the carbon nanotube composite
preform to a temperature ranging from about 110° C. to about
150° C. for a period of about 2-20 hours, whereby the liquid-state
thermosetting polymer becomes solidified; and S4414 cooling the carbon
nanotube composite preform to room temperature, and removing the carbon
nanotube composite preform from the die to obtain the carbon nanotube
composite.

[0158]It can be understood that in the step S44, the carbon nanotube
composite preform can be heated directly into the temperature ranging
from about 110° C. to about 150° C. Examples of method of
making the carbon nanotube composite are taught by US PGPub.
20090155467A1 to Wang et al. The methods and carbon nanotube composites
taught therein are hereby incorporated by reference.

[0159]As described above, the planar heater 10 can be a flat stacked-type
heater, which uses a carbon nanotube composite structure as a heating
element 16 whose performance is further improved by the presence of the
matrix. Selectively, the heat-reflecting layer 17, the supporter 18, the
protecting layer 15 can be applied according to practical needs.

Hollow Heater/Three-dimensional Heater

[0160]Referring to FIGS. 19 and 20, a hollow heater 20 is shown. The
hollow heater 20 includes a hollow supporter 28, a heating element 26, a
first electrode 22, a second electrode 24, and a heat-reflecting layer
27. The heating element 26 is disposed on an outer circumferential
surface of the hollow supporter 28. The heat-reflecting layer 27 is
disposed on an outer circumferential surface of the heating element 26.
The hollow supporter 28 and the heat-reflecting layer 27 are located at
two opposite circumferential surfaces of the heating element 26. The
first electrode 22 and the second electrode 24 are electrically connected
to the heating element 26 and spaced from each other. In one embodiment,
the first electrode 22 and the second electrode 24 are located on
opposite ends of the heat-reflecting layer 27.

[0161]The hollow supporter 28 is configured to support the heating element
26 and the heat-reflecting layer 27. The hollow supporter 28 defines a
hollow space 282. The shape and size of the hollow supporter 28 can be
determined according to practical demands. For example, the hollow
supporter 28 can be shaped as a hollow cylinder, a hollow ball, or a
hollow cube. Other characters of the hollow supporter 28 are the same as
the planar supporter 18 disclosed herein. In one embodiment, the hollow
supporter 28 is a hollow cylinder.

[0162]The heating element 26 can be attached on the inner surface or
wrapped on the outer surface of the hollow supporter 28. In the
embodiment shown in FIGS. 20 and 21, the heating element 26 is disposed
on the outer circumferential surface of the hollow supporter 28. The
heating element 26 can be fixed on the hollow supporter 28 with an
adhesive (not shown) or by a mechanical force. Similar to the heating
element 16 discussed above, the heating element 26 also includes a carbon
nanotube composite structure. The carbon nanotube composite structure can
include a matrix and one or more carbon nanotube structures. The
characters of the carbon nanotube structure are the same as the carbon
nanotube structure disclosed in the above. All embodiments of the carbon
nanotube structure discussed above can be incorporated into the hollow
heater 20. Same as disclosed herein, the carbon nanotube structure can be
a carbon nanotube film structure, a linear carbon nanotube structure or a
combination thereof

[0163]The heating element 26 can be a layer-shaped carbon nanotube
composite structure, a linear carbon nanotube composite structure or
combinations thereof Referring to FIG. 21, the heating element 26 can
include a carbon nanotube film structure 262 wrapped on a surface of the
hollow supporter 28 and a matrix 264 dispersed in the micropores of the
carbon nanotube film structure 262. Referring to FIG. 22, the heating
element 26 can include a matrix 264 wrapped on a surface of the hollow
supporter 28 and a carbon nanotube film structure 262 entirely enclosed
in the matrix 264. Referring to FIG. 23, when the heating element 26
includes a single linear carbon nanotube composite structure 260, the
single linear carbon nanotube composite structure 260 can spirally twist
about the hollow supporter 28. In another example, referring to FIG. 24,
when the heating element 26 includes two or more linear carbon nanotube
composite structures 260, the linear carbon nanotube composite structures
260 can be disposed on the surface of the hollow supporter 28 and
parallel with each other. The linear carbon nanotube composite structures
260 can be disposed side by side or separately. In another example shown
in FIG. 25, when the heating element 26 includes a plurality of linear
carbon nanotube composite structures 260, the linear carbon nanotube
composite structures 260 can be knitted to obtain a net disposed on the
surface of the hollow supporter 28. It is understood that these linear
carbon nanotube composite structures 260 can be applied to the inside of
the supporter 28.

[0164]The first electrode 22 and the second electrode 24 can be disposed
on a same surface or opposite surfaces of the heating element 26.
Furthermore, it is imperative that the first electrode 22 can be
separated from the second electrode 24 to prevent short circuit of the
two electrodes 22, 24. The first electrode 22 and the second electrode 24
can be the same as the first electrode 12 and the second electrode 14
discussed above. All embodiments of the electrodes discussed herein can
be incorporated into the hollow heater 20. In the embodiment, the first
electrode 22 and the second electrode 24 are both wire ring surrounded
the heating element 26 and parallel with each other. And each of the
first electrode 22 and the second electrode 24 includes a linear carbon
nanotube structure. The linear carbon nanotube structures disposed on the
two ends of the heating element 26, and wrap the heating element 26 to
obtain two wire rings.

[0165]The heat-reflecting layer 27 can be located on the inner surface of
the hollow supporter 28, and the heating element 26 is disposed on the
inner surface of the heat-reflecting layer 27 as shown in FIG. 26. The
heat-reflecting layer 27 can be located on the outer surface of the
hollow supporter 28, and the heating element 26 is disposed on the inner
surface of the hollow supporter 28 as shown in FIG. 27. Alternatively,
the heat-reflecting layer 27 can be omitted. Without the heat-reflecting
layer 27, the heating element 26 can be located directly on the hollow
supporter 28. The other properties of the heat-reflecting layer 27 are
the same as the heat-reflecting layer 17 discussed above.

[0166]When one of the inner circumferential and the outer circumferential
surfaces of the heating element 26 is exposed to air, the hollow heater
20 can further include a protecting layer (not shown) attached to the
exposed surface of the heating element 26. The protecting layer can
protect the hollow heater 20 from the environment. The protecting layer
can also protect the heating element 26 from impurities. In one
embodiment, the heating element 26 is disposed between the hollow
supporter 28 and the heat-reflecting layer 27 as shown in FIG. 19,
therefore a protecting layer would not necessarily be needed.

[0167]In use of the hollow heater 20, an object that will be heated can be
disposed in the hollow space 282 (shown in FIG. 20). When a voltage is
applied to the first electrode 22 and the second electrode 24, the carbon
nanotube structure of the heating element 26 of the hollow heater 20
generates heat. As the object is disposed in the hollow space 282, the
whole body of the object can be heated evenly.

[0168]Referring to FIG. 28, an embodiment of a method for making the
hollow heater 20 includes the steps of: [0169]M1: making a carbon
nanotube structure having a plurality of micropores; [0170]M2: connecting
a first electrode 22 and a second electrode 24 to the carbon nanotube
structure;

[0171]M3: fixing the carbon nanotube structure on a surface of a hollow
supporter 28; and [0172]M4: supplying a material into the carbon
nanotube structure to achieve a carbon nanotube composite.

[0173]It is to be understood that, after step M4, an additional step of
applying a protecting layer to cover the carbon nanotube composite can be
carried out. The protecting layer can be obtained by a sputtering method
or a coating method.

[0174]In step M1, the detailed process of making the carbon nanotube
structure is the same as the step S1 disclosed herein.

[0175]The detailed process of M2 can be the same as the step S2 discussed
above.

[0176]In step M3, the carbon nanotube structure can be fixed on an inner
or an outer surface of the hollow supporter 28 with an adhesive or by
mechanical method. The carbon nanotube structure can wrap the outer
surface of the hollow supporter 28. It is to be understood that, in one
embodiment, before fixing the carbon nanotube structure on the surface of
the hollow supporter, an additional step of applying a heat-reflecting
layer 27 attached to a surface of the hollow supporter 28 can be
performed. The heat-reflecting layer can be obtained on the outer surface
or the inner surface of the hollow supporter 28. And the carbon nanotube
structure is disposed on the surface of heat-reflecting layer 27, e.g.
the heat-reflecting layer is located between the hollow supporter 28 and
the carbon nanotube structure. The heat-reflecting layer 27 can be
applied by coating method, chemical deposition method, ion sputtering
method, and so on. In one embodiment, the heat-reflecting layer 27 is a
film made of aluminum oxide.

[0177]The detail process of the step M4 can be the same as the step S4
discussed above.

[0178]According to other embodiments, the method for making the hollow
heater 20 includes the steps of: [0179]M1': making a carbon nanotube
structure having a plurality of micropores; [0180]M2': connecting a first
electrode 22 and a second electrode 24 to the carbon nanotube structure;
[0181]M3': applying a material into the carbon nanotube structure to
achieve a flexible carbon nanotube composite; and [0182]M4': fixing the
flexible carbon nanotube composite on a surface of the hollow supporter
28.

[0183]In step M4', because the carbon nanotube composite is a flexible
carbon nanotube composite, the flexible carbon nanotube composite can be
curved and fixed on a surface of the hollow supporter 28.

[0184]It is to be understood that, in step M4', before fixing the flexible
carbon composite on a surface of the hollow supporter 28, an additional
steps of applying a reflecting layer 27 on the linear supporter 28 can be
performed. After step M4', an additional step of applying a protecting
layer on the flexible carbon composite, the first electrode 22 and the
second electrode 24 can be performed.

[0185]Referring to FIGS. 29, 30 and 31, a hollow heater 200 is provided
according to other embodiments. The hollow heater 200 includes a heating
element 204, a first electrode 210, a second electrode 212, and a
heat-reflecting layer 208. The heating element 204 has a hollow cube
configuration. The first electrode 210 and the second electrode 212 are
electrically connected to the heating element 204 and spaced from each
other. The first electrode 210 and the second electrode 212 are wire
shaped and extend from a bottom end of the heating element 204 to a
position higher above a top end of the heating element 204 for connecting
outer power supply when the hollow heater 200 is positioned in the
position shown in FIG. 31. The heat-reflecting layer 208 is disposed on
an outer circumferential surface of the hollow cube heating element 204.
The hollow heater 200 can include more than one first electrode 210 and
second electrode 212.

[0186]In detail, the hollow heater 200 has a rectangular cross-section.
The heating element 204 is attached on an inner surface of the
heat-reflecting layer 208 and also has a rectangular cross-section. A
pair of first electrodes 210 is disposed at first diagonal corners of the
rectangular cross-section of the heating element 204 and a pair of second
electrodes 212 is disposed at second diagonal corners of the rectangular
cross-section of the heating element 204. Thus, the first electrodes 210
and the second electrodes 212 are alternately arranged at the corners of
the rectangular cross-section of the heating element 204 in the hollow
heater 200. Each part of the heating element 204 between adjacent first
electrode 210 and second electrode 212 is controlled to produce heat
according to practical need by selectively supplying voltage to
corresponding first electrode 210 and second electrode 212. Additionally,
the hollow heater 200 can have two openings provided at opposite ends.
Alternatively, the hollow heater 200 may be designed to have only one
opening as shown in FIG. 31A. As shown in FIG. 31A, the hollow heater 200
has a bottom surface (not labeled). An object needed to be heated can be
put into the hollow heater 200 through the top opening and supported by
the bottom surface. Furthermore, a heating element 204 which is
electrically connected with two electrodes 214 can be located on the
bottom surface.

[0187]Referring to FIGS. 32 and 33, a hollow heater 300 is provided
according to other embodiments. The hollow heater 300 includes a hollow
supporter 302, a heating element 304, a first electrode 310, a second
electrode 312, and a heat-reflecting layer 308. The hollow heater 300 can
be a hollow hemisphere, hollow parabola or other shapes. The heating
element 304 is disposed on an outer circumferential surface of the hollow
supporter 302. The heat-reflecting layer 308 is disposed on an outer
circumferential surface of the heating element 304. In one embodiment,
the hollow heater 300 is a hollow hemisphere, the first electrode 310 is
round and disposed on bottom of the hemispherical hollow supporter 302.
The second electrode 312 is ring-shape and located on top of the
hemispherical hollow supporter 302. The first electrode 310 and the
second electrode 312 can be electrically connected to two conductive
wires 320, which extend through outside of the heat-reflecting layer 308.
In detail, the first electrode 310 is positioned at the lowest point of
the heating element 304 and is covered by the heat-reflecting layer 308.
The second electrode 312 encircles a top part of the heating element 304.
An inner surface of the hollow supporter 302 can be designed according to
an outer surface of the object needed to be heated, so that the inner
surface of the hollow supporter 302 can match the outer surface of the
object needed to be heated. This helps to reduce the thermal resistance
between the inner surface of the hollow supporter 302 and the outer
surface of the object needed to be heated.

Linear Heater

[0188]Referring to FIGS. 34, 35 and 36, a linear heater 30 is provided.
The linear heater 30 includes a linear supporter 38, a reflecting layer
37, a heating element 36, a first electrode 32, a second electrode 34,
and a protecting layer 35. The reflecting layer 37 is on the outer
surface of the linear supporter 38; the heating element 36 wraps the
surface of the reflecting layer 37. The first electrode 32 and the second
electrode 34 are separately connected to the heating element 36. In one
embodiment, the first electrode 32 and the second electrode 34 are
located on the heating element 36. The protecting layer 35 covers the
heating element 36, the first electrode 32 and the second electrode 34. A
diameter of the linear heater 30 is very small compared with a length of
itself. In one embodiment, the diameter of the linear heater 30 is in a
range from about 1 μm to about 1 cm. A ratio of length to diameter of
the linear heater 30 can be in a range from about 50 to about 5000.

[0189]The linear supporter 38 is configured for supporting the heating
element 36 and the heat-reflecting layer 37. The linear supporter 38 has
a linear structure, and the diameter of the linear supporter 38 is small
compared with a length of the linear supporter 38. Other characters of
the linear supporter 38 can be the same as the planar supporter 18 as
disclosed herein.

[0190]The heating element 36 can be attached on the surface of the linear
supporter 38 directly. When the heat-reflecting layer 37 wraps on the
surface of the linear supporter 38, the heating element 36 can be
attached on the surface of the heat-reflecting layer 37. The same as the
heating element 16 discussed above, the heating element 36 includes a
carbon nanotube composite structure. The carbon nanotube composite
structure can include a matrix and one or more carbon nanotube structure.
The characteristics of the carbon nanotube structure can be the same as
the carbon nanotube structure discussed above. The heating element 36 can
be located on surface of the linear supporter 38 like the heating element
26 on the surface of the hollow supporter 28 discussed above.

[0191]The first electrode 32 and the second electrode 34 can be disposed
on a same surface or opposite surfaces of the heating element 36. The
shape of the first electrode 32 or the second electrode 34 is not limited
and can be lamellar, rod, wire, and block among other shapes. In the
embodiment shown in FIGS. 33 and 34, the first electrode 32 and the
second electrode 34 are both lamellar rings. In some embodiments, the
carbon nanotubes in the heating element 36 are aligned along a direction
perpendicular to the first electrode 32 and the second electrode 34. In
other embodiments, at least one of the first electrode 32 and the second
electrode 34 includes at least one carbon nanotube film or at least a
linear carbon nanotube structure. In other embodiments, each of the first
electrode 32 and the second electrode 34 includes a linear carbon
nanotube structure. The linear carbon nanotube structures disposed on the
two ends of the heating element 36, and wrap the heating element 36 to
obtain two rings.

[0192]The protecting layer 35 is disposed on the outer surface of the
heating element 36. In one embodiment, the protecting layer 35 fully
covers the outer surface of the heating element 36. The heating element
36 is located between the protecting layer 35 and the heat-reflecting
layer 37.

[0193]Referring to FIG. 37, in other embodiments, the linear heater 30 can
include only a heating element 36, a first electrode 32, and a second
electrode 34. The first electrode 32 and the second electrode 34 are
separately connected to the heating element 36. The heating element 36 is
a linear carbon nanotube composite structure.

[0194]In use of the linear heater 30, the heater 30 can be spirally
twisted about a target, and the target will be heated from outside. The
heater 30 can also be inserted into the target to heat the target inside.
Given the small size of the linear heater 30, it can be used in
applications with limited space or in the field of MEMS for example.

[0195]Referring to FIG. 38, an embodiment of a method for making the
linear heater 30 includes the steps of: [0196]N1: making a carbon
nanotube structure having a plurality of micropores; [0197]N2: connecting
a first electrode 32 and a second electrode 34 to the carbon nanotube
structure; [0198]N3: fixing the carbon nanotube structure on a surface of
a linear supporter 38; and [0199]N4: supplying a material into the carbon
nanotube structure to achieve a carbon nanotube composite.

[0200]It is to be understood that, after N4, an additional step of
applying a protecting layer 35 on the carbon nanotube composite can be
provided.

[0201]In step N1, the detailed process of making the carbon nanotube
structure is the same as the step S1 disclosed herein.

[0202]The detailed process of N2 can be the same as the step S2 discussed
above.

[0203]In step N3, the carbon nanotube structure can be wrapped on the
surface of linear supporter 38 with an adhesive or by mechanical method.
When the carbon nanotube structure includes a plurality of carbon
nanotubes substantially oriented along a same direction, the oriented
direction can be from one end of the supporter 38 to another end of the
supporter 38. The first electrode and the second electrode are disposed
on the two ends of the linear supporter. It is to be understood that, in
one embodiment, before fixing the carbon nanotube structure on the
surface of the linear supporter 38, an additional step of applying a
heat-reflecting layer 37 attached to a surface of the linear supporter 38
can be performed. The heat-reflecting layer 37 can be applied on the
outer surface or the inner surface of the linear supporter 38. And the
carbon nanotube structure is disposed on the surface of heat-reflecting
layer 37, e.g. the heat-reflecting layer is located between the linear
supporter 38 and the carbon nanotube structure. The heat-reflecting layer
37 can be applied by coating method, chemical deposition method, ion
sputtering method, and so on. In one embodiment, the heat-reflecting
layer 37 is a film made of aluminum oxide.

[0204]The detail process of the step N4 can be the same as the step S4
discussed above.

[0205]According to other embodiments, the method for making the linear
heater 30 includes the steps of: [0206]N': making a carbon nanotube
structure having a plurality of micropores; [0207]N2': connecting a first
electrode 32 and a second electrode 34 to the carbon nanotube structure;
[0208]N3': applying a material into the carbon nanotube structure to
achieve a carbon nanotube composite; and [0209]N4': fixing the flexible
carbon nanotube composite on a surface of the linear supporter 38.

[0210]In step N4', because the carbon nanotube composite is a flexible
carbon nanotube composite, the flexible carbon nanotube composite can be
curved and fixed on a surface of the linear supporter 38.

[0211]It is to be understood that, in step N4', before fixing the flexible
carbon composite on a surface of the linear supporter, an additional
steps of applying a reflecting layer 37 on the linear supporter 38 can be
performed. After step N4', an additional step of applying a protecting
layer 35 on the heating element 36, the first electrode 32 and the second
electrode 34 can be performed.

[0212]The detail process of the step N3' can be the same as the step S4
discussed above.

[0213]It is to be understood that the above-described embodiments are
intended to illustrate rather than limit the invention. Variations may be
made to the embodiments without departing from the spirit of the
invention as claimed. It is understood that any element of any one
embodiment is considered to be disclosed to be incorporated with any
other embodiment. The above-described embodiments illustrate the scope of
the invention but do not restrict the scope of the invention.

[0214]Depending on the embodiment, certain of the steps of methods
described may be removed, others may be added, and the sequence of steps
may be altered. It is also to be understood that the description and the
claims drawn to a method may include some indication in reference to
certain steps. However, the indication used is only to be viewed for
identification purposes and not as a suggestion as to an order for the
steps.